Peristaltic pump assembly

ABSTRACT

A peristaltic pump assembly includes a cassette configured to be operatively engaged with a pump housing. A roller assembly is operatively disposed within a cavity formed into the cassette. The roller assembly includes a plurality of rollers that may be arranged in a planetary configuration around a drive shaft. At least one guide element is disposed about the periphery of the roller assembly and in engagement with at least a portion of an outer surface of each of the plurality of rollers. The guide element is configured to guide the plurality of rollers when the plurality of rollers is rotating.

BACKGROUND

The present disclosure relates generally to peristaltic pumps and, more particularly, to a peristaltic pump assembly.

Rotary-style peristaltic infusion pumps are often used to deliver fluid in a very controlled manner such as, for example, the intravenous delivery of medicine to a patient. These peristaltic pumps typically include a disposable pumping cassette and an assembly of radially arranged rollers received within a cavity of the cassette, wherein the rollers revolve together when rotationally driven by a drive shaft operated by a pump motor. A flexible tubing is disposed around a portion of the assembly of rollers and generally exerts a force against the rollers in contact therewith to thereby hold the rollers against the drive shaft.

In response to rotational movement of the rollers, portions of the flexible tube that are in contact with the rollers compress or otherwise occlude against a wall of the cassette. As a result, fluid traveling through the tube is temporarily trapped in the tube between the occluded points. The trapped fluid is released from the tube when the occlusion force on the tube is released. In this manner, fluid is urged through the tube via peristaltic wave action.

Sometimes a roller may not directly contact the tubing. In this instance, the roller(s) may undesirably move or shift and lose proper contact with the drive shaft. This could cause errors in various pumping operations, which may diminish the overall performance of the pump.

SUMMARY

Disclosed herein is a peristaltic pump assembly including a cassette configured to be operatively engaged with a pump housing. A roller assembly is operatively disposed within a cavity of the cassette and includes a plurality of rollers that may be arranged in a planetary configuration around a drive shaft. At least one guide element is disposed about the periphery of the roller assembly and in engagement with at least a portion of an outer surface of each of the plurality of rollers.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiment(s) of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical components. Reference numerals having a previously described function may or may not be described in connection with other drawings in which they appear.

FIG. 1 is a semi-schematic perspective view of an example of a rotary-style peristaltic infusion pump with an example of a cassette received therein;

FIG. 2 is a semi-schematic top view of a disposable pump cassette showing an assembly of rollers in an example position;

FIG. 2A is a semi-schematic, cutaway top view of a disposable pump cassette showing the assembly of rollers in another example position;

FIG. 3 is a side view of an example configuration of a roller for the roller assembly;

FIG. 4 is a perspective view of an assembly of a plurality of rollers and an example of a guide element; and

FIG. 5 is a cutaway top view of the peristaltic pump of FIG. 1.

DETAILED DESCRIPTION

Embodiment(s) of the peristaltic pump assembly as disclosed herein advantageously guide and/or locate a plurality of rollers of a roller assembly in response to rotational movement of a drive shaft to thereby maintain contact of the rollers with the drive shaft. The guide element may also improve the overall performance of the peristaltic pump by, for example, enabling the pump to achieve higher precision in fluid volume delivery. The guide element is also relatively simple to incorporate into the pump assembly.

With reference now to the drawings, FIG. 1 provides a rotary-style peristaltic infusion pump 10 including a disposable pump cassette 12 operatively disposed within a cassette receiving cavity (not shown) formed into a pump housing 14. A pump motor 16, disposed below the pump housing 14, powers rotational movement of a drive shaft 18. The drive shaft 18 extends through a bore (not shown) formed in the pump housing 14, through the cassette receiving cavity, and through a bore (not shown) formed in the cassette 12.

As shown in FIG. 2, the cassette 12 includes a base 22 and a wall 24, thereby defining a generally cylindrically-shaped cavity 26 therein. A flexible or otherwise compressible tubing 28 is disposed through an inlet 30 of the cassette 12, around a substantial portion of an inner surface 32 of the wall 24, and through an outlet 34. The tubing 28 is generally disposable and is often made of a polymeric material, non-limiting examples of which include silicones, AUTOPRENE (an opaque thermoplastic rubber with high wear resistance derived from SANTOPRENE, commercially available from Advanced Elastomer Systems, a subsidiary of ExxonMobil Chemical located in Houston, Tex.), VITON (a black fluoroelastomer with resistance to concentrated acids, solvents, ozone, radiation and temperatures up to 200° C. with good chemical compatibility, commercially available from DuPont Performance Elastomers located in Wilmington, Del.), TYGON (good chemical resistance with a clear finish, commercially available from Saint-Gobain Performance Plastics Corporation located in Akron, Ohio), PROTHANE II (a transparent, blue, polyester, polyurethane tubing with good chemical resistance, commercially available from Randolph Austin Company located in Manchaca, Tex.), and/or the like, and/or combinations thereof. The inner diameter of the tube 28 may be selected based on the desirable flow rates and the desirable viscosities of the fluid that will flow therethrough.

Referring also to FIGS. 3 and 4, an assembly 36 of satellite rollers 38 is received within the cavity 26 of the cassette 12 and located adjacent to and abutting a substantial portion of the tubing 28. Each roller 38 includes a generally cylindrically-shaped body 42 including an outer surface 40 and an inner surface 41, a spacing or cavity 44 defined by the inner surface 41, and two generally cylindrically-shaped ends 46, 48. At least a portion of the outer surface 40 of the roller 38 may be contoured (as best shown in FIG. 3). In an embodiment, the end 46 is a closed end, and the end 48 is an open end. It is to be understood that the rollers 38 rotate both individually and rotate as an assembly inside the cavity 26 of the cassette 12.

The rollers 38 are radially arranged in the cavity 26 around the drive shaft 18 that protrudes into the cavity 26 through the bore (not shown) formed into the base 22 of the cassette 12. As shown in FIG. 2, the assembly 36 of rollers 38 may be arranged in a planetary configuration with respect to the drive shaft 18. In an embodiment, the rollers 38 are made from a polymeric material such as, for example, acetal, polytetrafluoroethylene (e.g., Teflon® manufactured by E. I. du Pont de Nemours and Company, Wilmington, Del.), or the like, or combinations thereof. However, it is to be understood that any suitable material may be used, as desired.

In an embodiment, e.g., as shown in FIG. 3, the rollers 38, 38′ may include a radial flange 49 formed on one or both cylindrically-shaped ends 46′, 48′, where the radial flange 49 protrudes radially outwardly from the periphery of the ends 46′, 48′. The outer surface 40 of the rollers 38 may include an annular notch 51 formed therein, substantially adjacent to at least one of the flanges 49. The annular notch(es) 51 are configured to retain the guide element(s) 50 in a desirable operating position when placed over the roller assembly 36. As disclosed further herein, e.g., in connection with FIG. 4, the radial flange 49 and/or the annular notch 51 allow(s) the guide element 50 to engage the rollers 38, and substantially prevent(s) the guide element(s) 50 from slipping off of the roller assembly 36. Further, as mentioned above, the rollers 38 may have a contoured outer surface 40, and this surface 40 may also be configured to facilitate retention of the guide element(s) 50 in a desirable operating position when placed over the roller assembly 36.

The drive shaft 18 is generally knurled, roughened, and/or etched, or otherwise configured to frictionally engage the outer surface 40 of each roller 38, 38′ upon rotation of the drive shaft 18. The roller assembly 36 (i.e., the rollers 38, 38′ operating as a single unit) thus rotates in response to rotational movement of the drive shaft 18.

When the pump 10 is operating, rotational movement of the roller assembly 36 pumps the liquid through the tubing 28 to create a pressurized flow thereof. The tubing 28 compresses or otherwise occludes at a number of points in contact with the rollers 38, 38′ when the roller assembly 36 and the individual rollers 38, 38′ are all rotating. Fluid is trapped in the tubing 28 between two points of occlusion (i.e., from one roller 38, 38′ to an adjacent roller 38, 38′). The trapped fluid is passed or moved through the tubing 28 via peristaltic wave action at a flow rate determined by the rotational rate (rpm) of the drive shaft 18, and released when the tubing 28 is no longer occluded by the rollers 38, 38′.

In every revolution of the roller assembly 36, each roller 38, 38′ disengages the tubing 28 generally between the five o'clock and the seven o'clock positions (e.g., as shown in FIG. 2).

As shown in FIG. 2A, a roller 38′ is located at the six o'clock position (i.e., a position between the five o'clock and the seven o'clock positions). Since (in this position) the tubing 28 is not generating a radially inward force against the roller 38′ to hold the roller 38′ against the drive shaft 18, the roller 38′ may, in some instances, shift or slightly move within the cavity 26. As such, the roller 38′ may lose desirable contact with the drive shaft 18 and may slip when the drive shaft 18 rotates. This situation may, in some instances, deleteriously affect the overall performance of the peristaltic pump 10.

Referring now to FIG. 4, contact between the rollers 38, 38′ and the drive shaft 18 may be improved upon by disposing a guide element 50 about the periphery of the roller assembly 36. The guide element 50 suitably maintains the rollers 38, 38′ in a desirable position relative to the drive shaft 18, whereby reduction in lateral movement of the rollers 38, 38′ is achieved when the plurality of rollers 38, 38′ is rotating or otherwise moving.

The guide element 50 may be described as a continuous member that surrounds the entire periphery of the roller assembly 36. In an embodiment, the guide element 50 may be two bands (e.g., O-rings), each band having a substantially circular cross section (though it is to be understood that any suitable cross-sectional shape may be used, if desired), with a diameter ranging from about 0.5 mm to about 0.7 mm (though, similarly, it is to be understood that any suitable cross-sectional size may be used, if desired). As shown, guide elements 50 may be received within the annular notch(es) 51, if desired, to further aid in retaining the guide element(s) 50 in a desirable position. Although two guide elements 50 are shown in FIG. 4, it is to be understood that one, or more than two guide elements 50 may be operatively disposed about the periphery of the roller assembly 36. The guide element(s) 50 may have any suitable width, but generally do not overlap with each other (if more than one guide element 50 is used). Further, other configurations and/or constructions of the guide element 50 are also contemplated as being within the purview of the present disclosure, non-limiting examples of which include one or more washer(s), and/or the like, and/or combinations thereof.

The guide element 50 may be fabricated from any suitable elastomeric material. In a non-limiting embodiment, the guide element 50 is formed from polymeric materials, e.g., silicones, natural or synthetic rubbers, and/or the like, and/or combinations thereof. The polymeric materials are generally flexible.

The guide element 50, formed from the selected elastomeric material(s), is stretched around the rollers 38, 38′, and generally provides a force that pushes the rollers 38, 38′ into suitable contact with the drive shaft 18. The guide element 50 is generally useful when the rollers 38, 38′ are not in contact with the tubing 28 (e.g., at about the “6 o'clock” position) and may lose contact with the drive shaft 18. This is the position at which the rollers 38, 38′ (if they did not have guide element 50 therearound) may stall and may then cause a jam when the roller 38, 38′ behind the stalled one tries to push it along. Thus, the guide element 50 generally engages the outer surface 40 of the rollers 38, 38′, wherein any friction between the outer surface 40 and the guide element 50 is overcome by driving forces of the drive shaft 18. The guide element(s) 50 also rotate as the rollers 38, 38′ rotate, similar to a belt in a pulley.

In an embodiment, the guide element 50 is formed from an elastomeric polymeric material wherein the material is configured to stretch a predetermined amount beyond its relaxed state so as to minimize the normal force created. In contrast, higher normal forces created by stretching the material more than the predetermined amount may in some instances require an undesirable amount of power to drive the rollers, which may in turn undesirably reduce the battery life. In an embodiment, the predetermined amount is about 5% beyond the material's relaxed state.

Still referring to FIG. 4, the roller assembly 36 including the guide element(s) 50 may be assembled by slipping or otherwise placing the guide element 50 over one of the ends 46, 48 of rollers 38, 38′ of the roller assembly 36. The outer surface 40 of the rollers 38, 38′ is generally configured to retain the guide element 50. In an embodiment, if the assembly 36 includes the configuration of the rollers 38′ as depicted in FIG. 3 (wherein the outer surface 40 of the rollers 38′ includes at least one radial flange 49), the guide element 50 (e.g., if made from a flexible polymeric material) may be stretched and then slipped over the radial flange 49 (and into annular notch(es) 51, if provided).

In other embodiments, as mentioned above, one, or more than one guide element 50 may be placed or otherwise disposed about the periphery of the roller assembly 36. The one or a plurality of guide elements 50 may be situated in any position against the outer surface 40 of the rollers 38, 38′; however, the guide element(s) 50 should generally not be in a position where the tubing 28 comes into contact with the rollers 38, 38′.

With reference now to FIG. 5, an example of a method of assembling a portion of the peristaltic pump 10 is shown. The drive shaft 18 protrudes through a bore formed into the pump housing 14 and through the cavity 26 of the cassette 12. In the cassette 12, the tubing 28 is fed through the inlet 30, around the inner surface 32 of the wall 24, and through the outlet 34. The guide element(s) 50 are placed in contact with the outer surface 40, adjacent to the flange(s) 49 of the rollers 38, 38′ in the roller assembly 36. The roller assembly 36, including the guide element(s) 50, is placed within the cavity 26, wherein the rollers 38, 38′ are in frictional engagement with the drive shaft 18 and also abut (in some positions) a portion of the tubing 28. A cover (not shown) may be disposed over the roller assembly 36 and may be latched or otherwise fixed to the wall 24 of the cassette 12.

While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting. 

1. A peristaltic pump assembly, comprising: a cassette configured to be operatively engaged with a pump housing, wherein the cassette includes a cavity formed therein; a roller assembly operatively disposed within the cavity of the cassette, the roller assembly including a plurality of rollers arranged around a drive shaft, wherein each of the plurality of rollers includes an outer surface; and at least one guide element disposed about at least a portion of a periphery of the roller assembly and in engagement with at least a portion of the outer surface of each of the plurality of rollers.
 2. The assembly as defined in claim 1 wherein the at least one guide element is a continuous member.
 3. The assembly as defined in claim 1 wherein the at least one guide element surrounds the entire periphery of the roller assembly.
 4. The assembly as defined in claim 1 wherein the at least one guide element is one of a ring or a washer.
 5. The assembly as defined in claim 1 wherein the at least one guide element is fabricated from elastomeric materials.
 6. The assembly as defined in claim 1, wherein the at least one guide element is fabricated from an elastomeric material configured to stretch a predetermined amount beyond its relaxed state so as to minimize the normal force created.
 7. The assembly as defined in claim 6 wherein the predetermined amount is about 5%.
 8. The assembly as defined in claim 5 wherein the elastomeric materials are polymeric materials selected from silicones, natural or synthetic rubbers, and combinations thereof.
 9. The assembly as defined in claim 1 wherein the roller assembly rotates as a single unit while the at least one guide element is disposed about the periphery thereof.
 10. The assembly as defined in claim 1 wherein each of the plurality of rollers includes an axis of rotation such that each roller rotates individually while the at least one guide element is disposed about the periphery of the roller assembly.
 11. The peristaltic pump assembly as defined in claim 1 wherein the outer surface of each of the plurality of rollers is configured to retain the at least one guide element.
 12. The assembly as defined in claim 1 wherein the at least one guide element is configured to guide the plurality of rollers when the plurality of rollers is rotating, and wherein the at least one guide element is an O-ring.
 13. The assembly as defined in claim 1 wherein each of the plurality of rollers has two opposed ends and at least one radial flange protruding outwardly from at least one of the two opposed ends, and wherein the at least one radial flange is configured to retain the at least one guide element.
 14. The assembly as defined in claim 1 wherein each of the plurality of rollers has two opposed ends and at least one annular notch defined in each of the rollers substantially adjacent at least one of the two opposed ends, and wherein the at least one annular notch is configured to retain the at least one guide element.
 15. A method for guiding a plurality of rollers for a peristaltic pump, the peristaltic pump including a drive shaft, the method comprising: arranging the plurality of rollers around the drive shaft, wherein each of the plurality of rollers includes an outer surface; disposing at least one guide element about a periphery of the arranged plurality of rollers and in engagement with at least a portion of the outer surface of each of the plurality of rollers; and rotating the drive shaft to impart rotational movement to the roller assembly.
 16. The method as defined in claim 15, further comprising configuring the outer surface of each of the plurality of rollers to retain the at least one guide element.
 17. The method as defined in claim 15, further comprising guiding the plurality of rollers when the plurality of rollers is rotating, wherein the at least one guide element is an O-ring.
 18. The method as defined in claim 15, further comprising maintaining frictional contact between the plurality of rollers and the drive shaft.
 19. The method as defined in claim 15, further comprising: rotating the roller assembly as a single unit while the at least one guide element is disposed about the periphery thereof; and rotating the plurality of rollers individually while the at least one guide element is disposed about the periphery of the roller assembly.
 20. The method as defined in claim 18 wherein frictional contact between the plurality of rollers and the drive shaft is maintained by the guiding of the plurality of rollers. 